In recent years, what are required are that power converters output a large current and are formed with a small size. If the power converter is intended to output a large current, the heat generated by a power semiconductor device built in the power semiconductor module is increased. Thus, unless the heat capacity of the power semiconductor module or the power converter is large enough, it will reach the heat resistant temperature of the power semiconductor device, thus impeding miniaturization thereof. There has been developed a double sided cooling power semiconductor module which improves its cooling efficiency by cooling down the power semiconductor device from the both sides.
To cool down the double sided cooling power semiconductor module, both main surfaces of the power semiconductor device are sandwiched by lead frames as plate conductors, and a coolant is thermally connected with one surface of one lead frame on the opposite side of a surface opposed to the main surface of the power semiconductor device. Patent literature 1 discloses the invention of a double sided cooling power semiconductor module. In the module, the both main surfaces of the power semi conductor device included in an upper arm and a lower arm of an inverter circuit are sandwiched by the lead frames as the plate conductors. The module has upper and lower arm series circuits in which the upper and lower arms of the inverter circuit are connected in series. In the module, DC positive electrode wirings and DC negative electrode wirings extending from the conductors are parallel and opposed to each other. A resin encapsulation member is arranged therebetween, thereby reducing the wiring inductance while ensuring the insulation, and thus miniaturizing the module.
In enlargement of the current of the power converter, loss reduction of the power semiconductor device is a subject to be attained. To realize this, it is necessary to perform, high-speed switching of the power semiconductor devices with reduced loss. For the high speed switching, it is necessary to re strain the surge voltage generated by the wiring inductances in the wiring conductors of the inverter circuit. To reduce the wiring inductances as the root cause of the surge voltage, an effective structure is to align closely transient currents flowing in opposite directions, and is well known as a laminate structure of the DC positive electrode and the DC negative electrode. However, as the enlargement of the current of the power converter, a further reduction of the wiring inductances is required, at the terminal parts transmitting the DC power supplied to the power semiconductor module.